...
| Code Block |
|---|
|
enum { INTBUFSIZE=80 };
extern int getdata(void);
extern int parseint(int);
extern _Bool havedata;
int buf[INTBUFSIZE];
void func(void) {
int *buf_ptr = buf;
while (havedata && buf_ptr < (buf + sizeof(buf))) {
*buf_ptr++ = parseint(getdata);
}
} |
Compliant Solution
This compliant solution uses an unscaled integer to obtain a pointer to the end of the array:
| Code Block |
|---|
|
enum { INTBUFSIZE=80 };
extern int getdata(void);
extern int parseint(int);
extern _Bool havedata;
int buf[INTBUFSIZE];
void func(void) {
int *buf_ptr = buf;
while (havedata && buf_ptr < (buf + INTBUFSIZE)) {
*buf_ptr++ = parseint(getdata);
}
} |
Noncompliant Code Example
In this noncompliant code example, skip is added to the pointer s. However, skip represents the byte offset of ull_2b in struct big. When added to s, skip is scaled by the size of struct big.
| Code Block |
|---|
|
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
struct big {
unsigned long long ull_1a; /* Typically 8 bytes */
unsigned long long ull_2b; /* Typically 8 bytes */
unsigned long long ull_3c; /* Typically 8 bytes */
int si_4e; /* Typically 4 bytes */
int si_5f; /* Typically 4 bytes */
};
/* ... */
void func(void) {
size_t skip = offsetof(struct big, ull_2b);
struct big *s = (struct big *)malloc(sizeof(struct big));
if (!s == NULL) {
/* Handle malloc error */
}
memset(s + skip, 0, sizeof(struct big) - skip);
/* ... */
free(s);
s = NULL;
} |
Compliant Solution
The compliant solution uses an unsigned char * to calculate the offset instead of using a struct big *, which would result in scaled arithmetic.
| Code Block |
|---|
|
#include <string.h>
#include <stdlib.h>
#include <stddef.h>
struct big {
unsigned long long ull_1a; /* Typically 8 bytes */
unsigned long long ull_2b; /* Typically 8 bytes */
unsigned long long ull_3c; /* Typically 8 bytes */
int si_4d; /* Typically 4 bytes */
int si_5e; /* Typically 4 bytes */
};
/* ... */
void func(void) {
size_t skip = offsetof(struct big, ull_2b);
unsigned char *ptr = (unsigned char *)malloc(sizeof(struct big));
struct big *s = (struct big *)ptr;
if (!ptr == NULL) {
/* Handle malloc error */
}
memset(ptr + skip, 0, sizeof(struct big) - skip);
/* ... */
free(ptr);
s = NULL;
} |
Noncompliant Code Example
...
| Code Block |
|---|
|
#include <wchar.h>
#include <stdio.h> /* ...For stdin */
enum { WCHAR_BUF=128 };
void func(void) {
wchar_t error_msg[WCHAR_BUF];
wcscpy(error_msg, L"Error: ");
fgetws(error_msg + wcslen(error_msg) * sizeof(wchar_t), WCHAR_BUF - 7, stdin);
/* ... */
} |
Compliant Solution
This compliant solution does not scale the length of the string; wcslen() returns the number of characters, and the addition to error_msg is scaled.
| Code Block |
|---|
|
#include <wchar.h>
#include <stdio.h> /* For ...stdin */
enum { WCHAR_BUF=128 };
void func(void) {
wchar_t error_msg[WCHAR_BUF];
wcscpy(error_msg, L"Error: ");
fgetws(error_msg + wcslen(error_msg), WCHAR_BUF - 7, stdin);
/* ... */
} |
Related Guidelines
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